The present invention pertains generally to boring bars and the like for machining surfaces concentric with the axis of bar rotation.
In existing boring bars it is the practice to position the cutting tool in incremental fashion as machining progresses with each tool adjustment requiring access to the tool station at a point along the bar. Considerable time is expended in gaining access to and positioning of a tool holder depending on the work piece and the type of mill carrying the boring bar.
Attempts at providing remotely positioned controls for positioning a tool holder radially of a boring bar are disclosed in U.S. Pat. No. 4,275,624 wherein a splined shaft extends lengthwise of a boring bar and engages a splined tool holder to impart movement to the holder radially of the bar. A control is located at the bar end and includes an internally threaded handwheel acting on a threaded rod which in turn axially positions the splined shaft. The splined shaft, as well as the tool holder, require the task machining of inter-engaging teeth or splines with the splines carrying thrust as well as rotational loads. Further, the pitch of the splines is such as to render tool removal for manual pre-positioning of the tool difficult. Further, a boring bar must be drilled lengthwise off center a substantial distance with such drilling requiring a great deal of precision to prevent backlash between bar and tool holder. A key and keyway prevent tool rotation.
U.S. Pat. No. 3,237,487 discloses a powered bar having a head thereon with rack and pinion components operable to radially position cutting tools.
U.S. Pat. No. 4,369,007 discloses a threaded tool holder with an internally threaded pinion imparting radial movement to same. A ratchet drive powers the pinion. The tool holder has flats thereon to prevent rotation.
U.S. Pat. No. 3,730,636 discloses a boring head for installation in a boring machine with the head having a bit positioned by a rack and pinion.
U.S. Pat. No. 3,073,186 discloses a boring bar tool with a threaded tool holder having flat surfaces formed thereon to retain the shank against rotation in the boring bar.
U.S. Pat. Nos. 2,484,480 and 4,761,103 disclose cutting tools positioned radially of the boring bar by reason of the tool being carried in a threaded holder in engagement with a worm wheel.